1. The Field of the Invention
The invention relates to methods, apparatus, and systems for managing storage sub-systems and networks. Specifically, the invention relates to methods, apparatus, and systems for managing Fast Replication capable storage sub-systems and networks.
2. The Relevant Art
Data processing systems often work with large amounts of data and require mechanisms to manage the storage and archiving of that data. For example, transaction processing systems typically access large databases and log results such as transaction records at a very high rate. The ability to quickly and reliably copy data from one storage area to another enables the deployment of efficient and reliable high-performance processing applications and systems.
Fast replication techniques such as IBM's Flashcopy™ technology have been developed in response to the need for efficient copying mechanisms within high-performance processing systems. A fast replication operation gives the appearance of an instantaneous copy, while the actual transfer of data is conducted as a background process, or is deferred until the data to be copied is about to be overwritten. With fast replication techniques, applications may conduct data snapshots (point-in-time copies) and continue processing rather than suspending operation while the data transfers occur.
In addition to increased performance, fast replication capable systems simplify the code complexity of I/O intensive processes such as those conducted on large mainframe systems and the like. System performance may also be increased in that support for fast replication operations may be provided by low-level drivers and devices that are optimized for performance.
Fast replication capable systems preferably support multiple concurrent fast replication data transfers. Since the data transfer may be deferred indefinitely, the act of initiating a fast replication operation between a source and a target volume is often referred to as “establishing a fast replication relationship.” Likewise, canceling a pending fast replication transfer may be referred to as “withdrawing a fast replication relationship.”
Without support for fast replication relationships, conducting a point-in-time copy often requires that a system suspend all tasks that access a source and/or target device. Since many systems do not have explicit knowledge of the devices that will be accessed by each task, those systems require suspension of all tasks except for the task conducting the actual fast replication operations. Suspension of the various tasks or processes in order to conduct fast replication operations greatly reduces the performance of multi-tasking systems.
One challenge of fast replication capable systems, particularly those systems capable of establishing multiple simultaneous fast replication relationships on a sub-volume basis, is maintaining synchronization between tasks conducting fast replication operations and the memory management or storage management processes of the operating system. Memory involved in a fast replication relationship cannot be safely allocated to other tasks until the actual data transfer has concluded. As a result, deleting data on fast replication capable storage subsystems typically requires mechanisms for detecting whether specific regions are involved in a fast replication relationship and whether the data transfers related to the fast replication relationship have occurred. Such means and methods place a heavy burden on the memory management or storage management processes of the operating system and typically reduce the performance of data processing systems, especially in systems where multiple fast replication processes may be occurring simultaneously.
Therefore, what is needed are methods and apparatus for managing storage that facilitate reuse of storage regions involved in a fast replication relationship and maintain synchronization with the storage management processes of the operating system. Specifically, methods and apparatus are needed that ensure safe withdrawal of any fast replication relationships active within specified regions of storage. Such methods and apparatus would preferably operate at a sub-volume level in a manner that is efficient, reliable, and straightforward to implement.